To limit the probability of an excessive number or inappropriate location of defects (such as knots, holes, decay, shake, wane and checks, crimps and the presence of sapwood), which could lead to a reduction in the watertightness of shingles exposed to the weather, which could lead to water penetrating directly to roof decking or sheathing, which could lead to deterioration, which could lead to the structural failure of roofs or assemblies protected by roofs, which could lead to harm to persons.